If you're type 1 diabetic or have Pernicious anaemia you have to manage injections, sometimes daily. Now there's hope for treating such chronic diseases via implants powered by nothing more than light-triggered engineered cells.

The implants could also monitor toxins in the body in real time, providing long-term health data — either warning you to take your heart meds or even administering the meds themselves.

The technology, reported in the journal Nature Photonics, consists of transparent polymer implants. Each implant has genetically modified cells that activate in response to light, and could be programmed to release chemicals.

Each hydrogel implant was 4 millimetres by 40 millimetres, and only a millimetre thick. The patches were loaded up with cells engineered to respond to light.

Choi and Yun demonstrated the implants in two ways. In one experiment they used them to deliver insulin, and in another they were toxin detectors.

The insulin system was used on diabetic mice. The scientists sent blue light through an optical fibre to the implant, inducing the cells in the implant to make a protein that stimulates insulin production.

For the toxin detection, the engineered cells emitted green light in the presence of heavy metals. By measuring the light levels from the implant, they could see how much heavy metal was present.

There is still work to be done before it gets to local clinics. First, the cells have to be taken from the host — otherwise there is the risk of immune reactions. Also, the transmission of light through the hydrogel has to be extended — humans are bigger than mice. Third, it will take time to discover how porous the hydrogels should be in order to best deliver the kinds of drugs necessary.

If that happens, one day our bodies could be networked as much as our devices.